Cutter head and method of forming same

ABSTRACT

A cutter head and a gear cutting machine of the type wherein a plurality of cutting tools are mounted in radially movable and circumferentially spaced relation upon the head, the cutter head being formed from an annular pressure plate, a plurality of uniformly dimensioned, wedge-shaped tool slot separators and a plurality of uniformly dimensioned, generally rectangular tool slot spacers alternately arranged upon the annular pressure plate to form slots for receiving the cutting tools, the separators and spacers being heat treated prior to assembly upon the annular pressure plate, the separators and spacers being accurately positioned upon the pressure plate by alignment dowels surrounded by soft metal plugs and extending through coaxial bores in the pressure plate and the respective separators and spacers.

United States Patent 1 [111 3,868,885 Menne et al. 1 Mar. 4, 1975 CUTTERHEAD AND METHOD OF FORMING SAME Inventors: Joseph D. Menne, Canton;George N. Sigulas, Peoria, both of 111.

Assignee: Caterpillar Tractor Co., Peoria, 111.

Filed: Feb. 1, 1974 Appl. No.: 438,538

Related U.S. Application Data Division ofSer. No. 317,162, Dec. 17,1973, Pat. No. 3,820,227.

U.S. Cl. 90/11 A, 90/10, 29/105 R Int. Cl 1323f 21/12 Field of Search90/11 R, 11 A, 1, 1.6,

References Cited UNITED STATES PATENTS 4/1944 Pelphrey 90/10 6/1965SOlSki et al. 29/105 8/1969 Birch 90/10 6/1971 Manthei 29/105 PrimaryE.raminer-Leonidas Vlachos Attorney, Agent, or FirmPhillips, Moore,Weissenberger Lempio & Strabala [57] ABSTRACT A cutter head and a gearcutting machine of the type wherein a plurality of cutting tools aremounted in radially movable and circumferentially spaced relation uponthe head, the cutter head being formed from an annular pressure plate, aplurality of uniformly dimensioned, wedge-shaped tool slot separatorsand a plurality of uniformly dimensioned, generally rectangular toolslot spacers alternately arranged upon the annular pressure plate toform slots for receiving the cutting tools, the separators and spacersbeing heat treated prior to assembly upon the annular pressure plate,the separators and spacers being accurately positioned upon the pressureplate by alignment dowels surrounded by soft metal plugs and extendingthrough coaxial bores in the pressure plate and the respectiveseparators and spacers.

2 Claims, 4 Drawing Figures CUTTER HEAD AND METHOD OF FORMING SAME Thisis a division of Ser. No. 317,162, filed Dec. 17, 1973, now U.S. Pat.No. 3,820,227.

BACKGROUND OF THE INVENTION The present invention relates to gearcutting machines of the type wherein a plurality of cutting tools aremovably mounted in radial slots formed in a cutter head. In this type ofmachine, the cutter head is moved axially with respect to a gear blankand the cutting tools are gradually moved radially inwardly until thedesired depth of cut is achieved.

Heretofore, the cutter heads have been formed as integral structureswith the tool slots being machined into the head, the head then beingheat treated to achieve the desired hardness.

Cutter heads formed by this method are relatively expensive due tothesubstantial machining required. In addition, excessive stress risersor concentrations tend to be formed during heat treating because of theunequal sections and radii in the cutter head.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to provide a cutter head design and a method of forming acutter head which overcome one or more of the problems set forth above.

It is a particular object of the present invention to form such a cutterhead from an annular pressure plate, a plurality of uniformlydimensioned tool slot separators and a plurality of uniformlydimensioned tool slot spacers which are separately heat treated prior toassembly in order to minimize stress concentrations.

It is a further object of the further invention to provide a cutter headand a method of forming a cutter head for a gear cutting machine whereinassembly of the cutter head is simplified with the separators andspacers being accurately positioned on the pressure plate by alignmentdowels surrounded by soft metal plugs extending through coaxial bores inthe pressure plate and the respective separators and spacers.

Additional objects and advantages of the present invention are madeapparent in the following description having reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1. is a plan view of a cutterhead according to the present invention.

FIG. 2 is a view taken along section lines Il-II of .FIG. 1.

FIG. 3 is a view taken along section line III-III of FIG. 1.

FIG. 4 is a fragmentary view with parts in section of a gear cuttingmachine of the type in which the present cutter head may be employed.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings,FIGS. 1-3 illustrate a cutter head 11 constructed according to thepresent invention. The cutter head 11 is preferably employed in a gearcutting machine of the type illustrated in FIG. 4. In such a machine,the cutter head supports a plurality of cutting tools in radiallymovable relation for forming a gear from a workpiece such as thatindicated at 12 in FIG. 4.

Details of the gear cutting machine other than the cutter head are notcritical to the present invention since the invention is directedparticularly toward the cutter head and its method of construction.However, a brief description of the gear cutting machine is setReferring again particularly to FIG. 4, the assembled cutter head 11 isbolted to a head plate 22 after which the cutting tools 21 are arrangedin the slots 17. Note that the tool slot separators 14 each form amounting bracket 14a by which the cutter head 11 is secured to the headplate 22. The cutter head 11 and head plate 22 are then placed in theheadstock 23 of the gear cut ting machine in abutting relation with anadapter 24 which is attached to the lower end ofa cutter head support26. The cutter head 11 and head plate 22 are held in place within theheadstock by means of a retaining ring 27 bolted to the lower end of theheadstock unit.

The entire headstock 23 is vertically movable for replacement of thetools 21, cutter head 11 or for the insertion or removal of theworkpiece or gear blank 12. When the headstock 23 is lowered into thework position illustrated in FIG. 4, the headstock housing 28 remainsfixed and thus establishes the vertical position of the cutter head 11.

The workpiece 12 is attached to a reciprocable ram which is partiallyindicated at 31. The workpiece is alternately raised and lowered pastthe cutting tools 21 during the machining or cutting operation.

The radial position of the cutters 21 is controlled by a reciprocablefeed conection or sleeve 32 carrying a feed cone member 33 and retractorring 34. The reciprocable sleeve 32 is connected to and synchronizedwith the reciprocable ram 31 for example by a conventionalcam-and-rachet type interconnection (not shown). Because of theinterconnection with the reciprocable ram, the sleeve 32, feed cone 33,and retractor ring 34, as viewed in FIG. 4 are moved downwardly anincremental amount prior to each cutting stroke so that the tools 21areadvanced radially inwardly to accomplish a somewhat deeper cut duringeach successive cutting stroke. Sleeve 32 is moved upwardly by thecam-and-rachet interconnection at the end of each cutting stroke, thusthe retractor ring 34 causes tools 21 to be moved radially outward andout of contact with workpiece 12 as it is lowered by ram 31 during thereturn stroke.

Referring now to FIGS. 1-3, the pressure plate 13 is annularly formed toprovide a central passage for receiving the workpiece 12. The pressureplate is also recessed to facilitate its mounting upon the adapter 24.As noted above, the cutter head also comprises a plurality of tool slotseparators 14 which are of uniformly dimensioned, wedge-shapedconstruction and a plurality of tool slot spacers 16 which are alsouniformly dimensioned and are of generally rectangular configuration. Itmay be noted that with the tool slot separators and spacers beingcircumferentially arranged about the pressure plate 13, the innersurfaces of the separators and spacers are curved to provide a circularopening through the assembled cutter head 11.

The uniform dimensions of both the spacers and separators is ofparticular importance to the present invention since the separatelyformed separators and spacers may be selectively heat treated along withthe pressure plate 13 to minimize the formation of stress risers orconcentrations in the parts. It may be seen by referring to FIG. 2, forexample, that the assembled cutter head has portions of substantiallyvarying thickness. In the prior art, where the entire cutter head hasbeen integrally formed and heat treated as a unit, the unequal sectionsand radii of the head have caused the formation of substantial stressrisers which have'resulted in early fatigue cracking of the cutter head.According to the present invention, the pressure plate, the respectiveseparators and the respective spacers are of substantially uniformthickness to permit selective heat treatment according to theirrespective sizes and material.

The pressure plate 13, the tool slot separator 14 and the tool slotspacers 16 are all preferably formed or fabricated from No. 16 pressuredie steel.

Also referring to FIGS. 2 and 3, it may be seen that the pressure plate,the separators and the spacers have holes penetrating completely orpartly therethrough to facilitate mounting of the separators and spacersupon the pressure plate. The holes are drilled and tapped as necessaryprior to heat treatment with the holes being plugged for example withclay during heat treatment to prevent the threads from becoming brittle.

Another feature of the present invention relates to the manner in whichthe tool slot separators and spacers are maintained in accuratealignment upon the pressure plate. This feature of the invention isparticularly important since it is necessary to maintain the cuttingtools 21 in accurate alignment within the gear cutting machineillustrated in FIG. 4.

The separators and spacers are preferably positioned and secured to thepressure plate by cap screws 41 which are threaded into tapped bores 42.The separators and spacers are held accurately positioned upon thepressure plate 13 by means of alignment dowels indicated for example at43 for both the separators and spacers. The alignment dowels 43 arearranged in oversized bores 44 which pass through the pressure plate andthe respective separators and spacers. Soft metal plugs 46, for exampleof mild steel, are pressed into the oversized bores with holes thenbeing drilled in the plugs to receive the alignment dowels.

Through the above-described procedure, the cutter head may be accuratelyassembled from the various parts including the pressure plate 13, thetool slot separators 14 and the tool slot spacers 16. The various partsare heat treated prior to assembly as described above. The separatorsand spacers are loosely bolted to the pressure plate by the cap screws41. The separators and spacers are then precisely located incircumferentially abutting relation and radial orientation in order toaccurately form the radial tool slots 17. To facilitate such location ofthe separators and spacers, the bores in pressure plate 13 for receivingmounting bolts 41 are approximately 0.015 inches oversize with respectto the bolt diameters. After alignment of the separators and spacers,the mounting bolts 41 are tightened. The soft metal plugs are thenpressed into the oversized bores and drilled to receive the dowels 43which insure that alignment is maintained.

After mounting bolts 41 are tightened and the alignment dowels 43 are inplace, the assembled cutter head 11 is subjected to a finish-grindingoperation.

Thus, the present invention provides a particularly simple and effectivemethod for forming an improved cutter head of the type described abovefor use within a gear cutting machine of the type illustrated in FIG. 4.

What we claim is:

1. A cutter head for a cutting machine of the type wherein cutting toolsare radially arranged in circumferentially spaced relation on the head,comprising an annular pressure plate, a plurality of uniformlydimensioned, wedge-shaped tool slot separators and a plurality ofuniformly. dimensioned, generally rectangular tool slot spacers, theseparators and spacers being alternately arranged in circumferential andabutting relation on the annular pressure plate, the separators having agreater thickness than the spacers to form a plurality of slots forreceiving the plurality of cutting tools, the uniformly dimensionedseparators and the uniformly dimensioned spacers being selectively heattreated prior to mounting on the pressure plate in order to minimizestress concentrations.

2. The cutter head of claim 1 wherein each of the separators and spacersis accurately positioned upon and secured to the pressure plate by screwmeans and at least one alignment dowel surrounded by soft metal plugmeans extending through coaxial bores in the pressure plate and therespective separator or spacer. l

1. A cutter head for a cutting machine of the type whErein cutting toolsare radially arranged in circumferentially spaced relation on the head,comprising an annular pressure plate, a plurality of uniformlydimensioned, wedge-shaped tool slot separators and a plurality ofuniformly dimensioned, generally rectangular tool slot spacers, theseparators and spacers being alternately arranged in circumferential andabutting relation on the annular pressure plate, the separators having agreater thickness than the spacers to form a plurality of slots forreceiving the plurality of cutting tools, the uniformly dimensionedseparators and the uniformly dimensioned spacers being selectively heattreated prior to mounting on the pressure plate in order to minimizestress concentrations.
 2. The cutter head of claim 1 wherein each of theseparators and spacers is accurately positioned upon and secured to thepressure plate by screw means and at least one alignment dowelsurrounded by soft metal plug means extending through coaxial bores inthe pressure plate and the respective separator or spacer.